When do I use आओगी and when आयेगी ? Is it plural versus singular?
"Aogi" is second person feminine. It is used when it is about the person you are talking to and if the person is a female. "Ayegi" is used for third person feminine-when you are talking about a third person who is female
i saw elsewhere that the correct form is आएगी
so is it both? we just get to choose?
Yes, the correct form is "आएगी" but when you speak both the word have same pronunciation.